1. Field of the Invention
The present invention relates to a power supply system and a power supply system control method.
2. Background Information
Japanese Laid-Open Patent Application No. 5-236608 discloses an example of a conventional electric automobile with a motor and a vehicle electric power supply system. The vehicle electric power supply system includes a plurality of battery blocks electrically connected to the motor. Such a conventional vehicle power supply system switches a connection state of the battery blocks between a series connection and a parallel connection to vary the output voltage from the battery blocks. More specifically, in cases where the required voltage is relatively small, the output voltage is reduced by connecting the battery blocks in parallel, while in cases where the required voltage is relatively large, the output voltage from the battery blocks is increased by connecting the battery blocks in series. Therefore, the efficiency of the system is increased. However, in such a conventional vehicle power supply system, it is necessary to suppress abnormal currents (e.g., inrush current or input surge currents) that are generated by the potential difference between the battery blocks and an inverter for the motor when the serial and parallel connections of the battery blocks are switched.
On the other hand, Japanese Patent No. 3558546 discloses another example of a conventional electric automobile in which a chopper circuit is disposed between an inverter and a power supply system that switches a connecting state of a plurality of battery blocks between the serial and parallel connections. In this conventional electric automobile, the chopper circuit maintains the voltage of the battery blocks at a substantially constant value, and eliminates the difference between the output voltage from the battery blocks and the required voltage of the inverter as necessary.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved power supply system and power supply system control method. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.